Created .gitignore.
Created pandoc-lineno to seperate editorial comments and line numbers
clean up pandoc-ednotes

Signed-off-by: Douglas Ligertwood <dfaligertwood@dunelm.org.uk>
Created pandoc-musicnotes for second order editorial notes
Changed power symbol for pandoc-musicnotes
Added pandoc-offsidenotes and modified sidenotes to accomodate.
Added pandoc-offsidenotes filter to marked_processor